Flame-proof polyolefin compositions

ABSTRACT

The invention concerns polyolefin compositions with high flame resistance. The compositions comprise (percent by weight): 
     A) from 20 to 60% by weight of a heterophasic olefin polymer composition comprising a crystalline olefin polymer (a) and an elastomeric olefin polymer (b), said composition (A) being optionally modified with at least one functional monomer in an amount from 0.005% to 0.6% by weight with respect to the total weight of the total composition; 
     B) from 15 to 40% by weight of one or more than one inorganic hydrated fillers; 
     C) from 12 to 40% by weight of one or more than one organic flame retardants containing nitrogen in the molecule; 
     D) from 0 to 40% by weight of one or more than one inorganic anhydrous fillers. 
     Possible applications include the use as insulating material in electric wires and cables and the use as waterproofing sheets for roofs and tunnels.

This application is the U.S. national phase of International ApplicationPCT/EP00/12888, filed Dec. 18, 2000.

The present invention concerns polyolefin compositions with high flameresistance. These compositions are suitable to be used in severalapplications, e.g. as insulating material in electric wires and cables,as extruded sheets for waterproofing roofs and tunnels, in manufacturingraceways and pipes, general purpose extruded articles and gaskets. Saidcompositions comprise a thermoplastic olefin polymer in admixture withan elastomeric olefin polymer, an inorganic hydrated filler capable torelease water at the combustion temperature of the composition, anorganic nitrogen-containing flame retardant compound and preferably aninorganic anhydrous filler. The polymeric components are preferablymodified with a small amount of a functional monomer to improve thecompatibility with the fillers. No crosslinking treatment is made on thecompositions of the invention. It is known that inorganic hydratedfillers, such as magnesium hydroxide and aluminum hydroxide, whenpresent in suitable amount in the polyolefin compositions afford toreach a good level of flame resistance.

In particular, said hydrated inorganic fillers improve the flameresistance of polyolefins as shown for instance by values of the L.O.I.(limiting oxygen index) as high as or even higher than 24-25%. Toperform so effectively, the inorganic hydrated fillers must be presentin relatively high amount, which involves a worsening of the physicalmechanical properties, surface appearance of the extruded articles andelectrical properties, in particular volume resistivity.

Inorganic anhydrous fillers are well-known inexpensive fillers, usefulto improve physical mechanical properties and extrusion propertieswithout a significant impairing of the excellent electrical propertiesof the olefin polymers.

Inorganic anhydrous and hydrated fillers do not produce smoke duringcombustion, are not corrosive and are not released from compositions ifexposed to water or humidity.

Nitrogen containing organic compounds are also known for their flameretardant activity. Melamine in particular is used as organic filler tofire retard polymeric materials. Its action is supposed to be based onthe dilution of the combustible gases from thermal degradation of thepolymeric matrix with incombustible gases from sublimation anddecomposition of melamine itself. The use of melamine has also theadvantage to decrease the specific weight of the fire retardedmaterials. On the other hand, melamine is slightly soluble in hot waterand is a relatively soft filler, which affects abrasion resistance offinal items and mechanical properties. The combined use of inorganichydrated fillers, inorganic anhydrous fillers and melamine compounds isshown in the Japanese published patent application Hei 7 (1995) 330980.This application describes compositions consisting of at least anelastomeric and usually crosslinked copolymer selected fromethylene/alpha-olefin, ethylene/alpha-olefin/diene and ethylene/vinylacetate copolymers and of a mixture of additives able to give a highflame resistance, such a mixture comprising per 100 parts of polymer byweight:

from 50 to 300 parts by weight of an hydrated metal oxide,

from 1 to 40 parts by weight of a melamine compound,

from 1 to 50 parts by weight of talc.

The compositions disclosed in said patent application contain thereforefrom 21 to 75% by weight of hydrated metal oxide and from 0.2 to 21% byweight of the melamine compound referred to the total weight of thecomposition, the ratio of the percentage amounts of these compoundsranging therefore from about 1 to about 375.

In the working examples of the same patent application the minimumamount of hydrated metal oxide is about 46% referred to the total weightof the composition and the minimum ratio of the percentage amount of thehydrated metal oxide to the percentage amount of the melamine amount isabout 4.7.

The total amount of the fillers in the polymeric compositions of saidpatent application is kept at a still acceptable low level, so avoidingan extreme worsening of the physical mechanical properties and of thevolume resistivity. The obtained compositions are usually crosslinked toreach the best balance of the physical mechanical properties and can beused in typical applications of the elastomeric polymers.

On the other hand it is desirable to get a good balance of the flameresistance and physical mechanical properties also in thenon-crosslinked polyolefin compositions comprising thermoplastic andelastomeric polymers.

Now the applicant has found that the best balance of flame resistance,physical mechanical properties, extrusion properties and volumeresistivity in the case of non-crosslinked polyolefin compositions isobtained when the amount of inorganic hydrated fillers is less than orat most equal to 40% by weight with reference to the total weight of thecomposition. The present invention concerns in particular polyolefincompositions comprising (percent by weight):

A) from 20 to 60%, preferably from 30 to 45% by weight of a heterophasicolefin polymer composition comprising a crystalline olefin polymer (a)and an elastomeric olefin polymer (b), said composition (A) beingoptionally modified with at least one functional monomer in an amountfrom 0.005% to 0.6% by weight, preferably from 0.01% to 0.3%, referredto the total weight of the total composition;

B) from 15 to 40%, preferably from 18 to 35% by weight of one or morethan one inorganic hydrated fillers;

C) from 12 to 40%, preferably from 22 to 35% by weight of one or morethan one organic flame retardants containing nitrogen in the molecule;

D) from 0 to 40%, preferably from 10 to 25% by weight of one or morethan one inorganic anhydrous fillers.

The compositions of the instant invention can be worked with themachines, in particular the extruders, normally used to work thethermoplastic polymers, without undergoing any subsequent thermosettingreaction. Moreover the compositions of the instant invention typicallyhave a limiting oxygen index higher than or equal to 25 and areclassified V0. V1 or V2 according to the UL 94 method (UnderwritersLaboratories, “vertical burning test method”), keeping at the same timea good level of the other desired properties.

The heterophasic olefin polymer composition A) preferably comprises: (a)a portion consisting either of a crystalline propylene homopolymer, inparticular isotactic polypropylene, or of one or more than onecrystalline copolymers of propylene with ethylene and/or otheralphaolefins, in particular C₄-C₁₀ alphaolefins e.g. 1-butene, 1-hexene,1-octene and 4-methyl-1-pentene, or of a mixture of said homopolymerwith said copolymers; and (b) a portion consisting of elastomeric olefincopolymer(s). Examples of said elastomeric olefin copolymers areethylene-alphaolefin copolymers and ethylene-alphaolefin-dieneterpolymers, wherein the alphaolefin preferably has 3 to 10 carbonatoms, e.g. propylene, 1-butene, 1-hexene, 1-octene and4-methyl-1-pentene and the diene preferably is 1,3-butadiene,1,4-hexadiene or 5-ethylidene-2-norbornene. In said elastomericcopolymers the ethylene content can range between 20 and 70% by weightwhereas the diene, if present, is usually less or at most equal to 10%by weight. Particular examples of heterophasic compositions suitable ascomponent A) are the heterophasic compositions comprising (percent byweight):

a) 10-60%, preferably 20-50%, of a propylene homopolymer with anisotacticity index value (determined as percent by weight of the polymerinsoluble in xylene at 25° C.) higher than 80, preferably between 90 and98, or a propylene crystalline copolymer with ethylene and/or C₄-C₁₀alphaolefins containing at least 85% of propylene and having anisotacticity index value of at least 80 or a mixture thereof;

b) 0-40%, preferably 2-40%, more preferably 2-25%, of a copolymerfraction containing ethylene and insoluble in xylene at 25° C.;

c) 15-90%, preferably 15-78%, more preferably 30-75%, of an ethylenecopolymer with propylene and/or C₄-C₁₀ alphaolefins and optionally adiene, containing 20-60% of ethylene and completely soluble in xylene at25° C.;

the total content of ethylene in the heterophasic composition being from15 to 60% by weight. Component b) is preferably an essentially linear,crystalline copolymer of ethylene with 0.5 to 20% by weight of propyleneand/or C₄-C₁₀ alphaolefins. Examples of alphaolefins, possibly includedin components a) and b), are 1-butene, 1-hexene, 1-octene and4-methyl-1-pentene. The diene content in component c), if any, isusually not higher than 10% by weight. Said heterophasic compositionsare preferably prepared by a sequential polymerization process in atleast two steps using highly stereospecific Ziegler-Natta catalysts.Component a) is generally formed in the initial polymerization stepwhereas components b) and c) are formed in at least one successivepolymerization step. Said process is particularly useful when componentb) contains beside ethylene the same alphaolefins as component c),including propylene which is a preferred one.

Suitable catalysts comprise in particular the reaction product of asolid component, including a titanium compound and an electron donatingcompound (internal electron donor) supported on magnesium chloride, withan aluminumtrialkyl compound and an electron donating compound (externalelectron donor). Preferably the titanium compound is titaniumtetrachloride. The internal donor is preferably selected from alkyl,cycloalkyl and aryl phthalates, in particular from diisobutyl phthalate,di-n-butyl phthalate and di-n-octyl phthalate. The external donor ispreferably selected from silicon compounds having at least one —ORgroup, where R is a hydrocarbon radical, e.g. diphenyl-dimethoxysilane,methyl-t-butyl-dimethoxysilane, diisopropyl-dimethoxysilane,cyclohexyl-methyl-dimethoxysilane, dicyclopentyl-dimethoxysilane andphenyl-trietoxysilane.

Examples of said heterophasic compositions, along with polymerizationprocesses and catalysts suitable for their preparation are described inthe granted European Patents No. 400333 and 472946.

Said heterophasic compositions can also be obtained by mechanical mixingof the components a), b) and c) at a temperature higher than theirsoftening or melting points. A mixture of the components b) and c) to bemechanically mixed with component a) can be prepared by copolymerizingethylene with propylene and/or a C₄-C₁₀ alphaolefin and possibly a dienein the presence of a catalyst as described above.

The compositions of the present invention comprising said heterophasicpolymer composition as component A) are quite suitable as insulatingmaterial for the coating of the electric cables, since they have highvalues of the elongation at break. Use of this property is also made inother applications such as the production of extruded sheets forwaterproofing roofs and tunnels, raceways and pipes, extruded articlesand gaskets.

Particularly preferred in the scope of the present invention aretherefore the polyolefin compositions wherein component A) is anheterophasic composition of the above said type and the values of theelongation at break of the total composition are at least 125%, morepreferably equal to or higher than 150%.

Component B) of the compositions of the instant invention consists, assaid before, of one or more than one inorganic hydrated fillers in theform of a powder. The compounds usable as component B) are capable torelease water when heated, with the consequent effect of subtractingheat to the combustion and diluting combustible gases deriving from thedegradation of the polymeric matrix. In particular these compounds arecapable to release water at a temperature equal to or higher than thecombustion temperature of the polyolefin composition which includesthem, such a combustion temperature being mainly determined by thenature of component A) and by the combustion environment.

Examples of said inorganic hydrated fillers are the metal hydroxides,e.g. Mg(OH)₂ or Al(OH)₃: salts like hydrated silicates, sulfates orcarbonates containing water in the crystalline lattice or on theirsurface, e.g. hydrated magnesium carbonate; hydrated metal oxides, e.g.hydrated silica or alumina and mixed hydrated oxides of silicon andaluminum, as well as the mixtures of these compounds. Preferred aremagnesium hydroxide, optionally mixed with hydrated magnesium carbonate,and aluminum hydroxide, most preferred is magnesium hydroxide. Particledimensions are those of the typical inorganic fillers for polymers, i.e.usually less than 20 micron.

Component C) of the compositions of the present invention consists, assaid before, of one or more than one organic compounds containingnitrogen, preferably selected from 1,3,5-triazines, urea, dicyandiamide,organic derivatives from these compounds or their salts. Most preferredcompounds are melamine, acetoguanamine, benzoguanamine, ethylenurea andethylenthiourea. Component D) of the compositions of the presentinvention consists of one or more than one inorganic anhydrous fillers.Examples of commonly used inert mineral fillers of this type are talc,calcined kaolin and some carbonates. Calcined kaolin, possibly after asuitable surface treatment, is preferred. The presence of these fillersimproves the dispersion of the other components in the compositions andlets extruded articles with an improved surface be obtained. Moreoverthey help in getting a better balance of mechanical and selfexstinguishing properties and in lowering the cost of the finalcomposition. Also electrical properties are fairly improved by thepresence of these fillers.

In order to improve the compatibility of the fillers with the polymericcomponents, component A) is usually modified with at least one polarfunctional monomer using a variety of methods to insert functional unitsin the polymer chains. For example, one can prepare a master polymer bygrafting at least one polar monomer onto a propylene polymer backbone byusing free radical initiators, such as organic peroxides, according tothe method described in U.S. Patent No. 4,350,797 or by treating apropylene polymer in the particulate form with the polar monomers andradical initiators as described in European patent 572028. In both casesthe master polymer so obtained is then blended in the molten state withcomponent A). Preferably but not necessarily, the propylene polymer usedin the preparation of said master polymer is the same as component A).It is also possible to blend the polar monomer(s) and radical initiatorsdirectly with the heterophasic component A) in the molten state. Suchblending step in the molten state is carried out according to any of theknown techniques, preferably operating in an inert atmosphere, such asunder nitrogen, and with conventional equipment, such as internal mixersor single or twin-screw extruders, the blending temperature beingpreferably 180° C. to 230° C.

Most common polar monomers used in the modification of component A)contain at least a group selected from the carboxyl group and itsderivatives. Preferred polar monomers are acrylic acid, methacrylicacid, itaconic acid, citraconic acid, fumaric acid, maleic acid andcorresponding anhydrides and esters, and the unsaturated silanes e.g.vinyltrimethoxysilane. Particularly preferred is maleic anhydride.Whatever the method used to modify component A), the content of thepolar monomers in the compositions of the present invention, whenpresent, is comprised between 0.005 and 0.6%, preferably between 0.01and 0.3% by weight, with reference to the total weight of the totalcomposition.

Examples of free radical initiators which can be used in themodification of component A) with polar monomers are benzoyl peroxide,di-ter-butyl peroxide, 2,5-dimethyl-2,5-bis(ter-butyl peroxy)-hexane andazobisisobutyronitrile. The amount of the free radical initiator isusually from 0.006 to 0.6% by weight, preferably from 0.01 to 0.3% byweight, of the total weight of the modifying polymer.

In addition to the above components the compositions of the presentinvention may include other ingredients commonly used with thethermoplastic polymers, e.g. pigments, thermal antioxidants, ultravioletabsorbers, processing aids, filler dispersants, oils and waxes.Particularly useful are the filler dispersants, such as alkyltitanatesand polydimethylsiloxanes, which are quite effective to improve surfaceaspect, mechanical properties and processing behaviour of thecompositions.

Particularly preferred are the compositions of the present inventioncontaining magnesium hydroxide, melamine and calcined kaolin, optionallyin the presence of maleic anhydride. Compared with the compositionscontaining only magnesium hydroxide and melamine, the said compositionshave a better balance of the physical mechanical properties related tothe formulation costs, depending on the application. This is the casee.g. of the extruded sheets for waterproofing roofs and tunnels.

The compositions of the present invention are usually prepared using aninternal mixer, e.g. a Banbury mixer, or a single screw extruder, e.g. aBuss extruder, or a double screw extruder, e.g. a Wemer extruder. Mixingtemperature is usually between 170° C. and 250° C.

The examples reported hereinafter are given just to illustrate theinstant invention and not to limit its scope. In the examples thefollowing components were used:

Heterophasic Composition No. 1:

Heterophasic composition having a MIL of 0.6-1 g/10 min with totalethylene content 20%, comprising (all percentages by weight):

a) 33% of a crystalline propylene random copolymer with 4.3% ofethylene, containing about 9% of a fraction soluble in xylene at 25° C.and having an intrinsic viscosity [η] of 1.5 dl/g;

b) 6% of an essentially linear ethylene/propylene copolymer with 94% ofethylene, totally insoluble in xylene at 25° C.; and

c) 61% of an amorphous ethylene/propylene copolymer containing 21% ofethylene, totally soluble in xylene at 25° C., and having an intrinsicviscosity [η] of 3.2 dl/g.

Heterophasic Composition No. 2:

Heterophasic composition having a MIL of 6 g/10 min, with total ethylenecontent 16%, comprising (all percentages by weight):

a) 48% of crystalline propylene random copolymer with 3.5% of ethylene,containing about 7.5% of a fraction soluble in xylene at 25° C.;

b) 5% of an essentially linear ethylene/propylene copolymer with 90% ofethylene, totally insoluble in xylene at 25° C.; and

c) 47% of amorphous ethylene/propylene copolymer with 21% of ethylene,totally soluble in xylene at 25° C., and having an intrinsic viscosity[η] of 2.3 dl/g.

Maleic Anhydride Additive No.1:

Heterophasic composition No. 1 in spherical form supporting 5% by weightof maleic anhydride and 1% by weight of2,5-dimethyl-2,5-di(tert-butylperoxy)hexane.

Maleic Anhydride Additive No. 2:

Heterophasic composition No. 1 grafted with 1% by weight of maleicanhydride.

BY-27: 50% Silicone Gum (polydimethylsiloxane), marketed by Dow Corning.

Magnifin H5: magnesium hydroxide, marketed by Martinsweerk.

Securoc C: magnesium carbonate hydroxide, marketed by Incemin.

Whitetex: calcined kaolin, marketed by Engelhard.

Spinflam ML94M: micronized melamine, marketed by Montell.

Zn stearate: zinc stearate, marketed by Sogis.

Lica 12: neoalkyl titanates, marketed by Kenrich.

Irganox B225:pentaerythritol-tetrakis[3(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]and tri(2,4-di-tert-butylphenyl)phosphite in equal amounts, marketed byCiba

Irganox 1010:pentaerythritol-tetrakis[3(3,5-di-tert-butyl-4-hydroxyphenyl)propionate],marketed by Ciba.

DSTDP (irganox PS802): distearyl thiodipropionate, marketed by Ciba.

All the compositions were obtained using a Banbury mixer, working at 90rpm and at a temperature of 200° C. In a typical run, components werecharged into the mixer altogether and the composition was dischargedafter 5 minutes mixing. Compositions were subsequently milled in orderto be transformed by injection molding, compression molding orextrusion.

To characterize the compositions, plaques 120×120×3 mm were compressionmolded. The conditions of the molding were the following: 220° C. for 5minutes without pressure and 3 minutes at 200 bar, followed by immediatecooling to 23° C.

The molecular and physical mechanical properties were determinedaccording to the following methods:

Ethylene content: I.R. spectoscopy

Intrinsic viscosity: measure in tetrahydronaphtalene at 135° C.

Percentage of polymer soluble in xylene:

2.5 g of polymer were dissolved in 250 ml of xylene at 135° C. underagitation. After 20 minutes the solution was cooled down to 25° C., withagitation, and then it was allowed to settle for 30 minutes. Theprecipitate was filtered with filter paper, the solution was evaporatedunder a nitrogen current, and the residue dried under vacuum at 80° C.to a constant weight. The weight percentage of polymer soluble in xyleneat room temperature was calculated.

Melt Index L ASTM D-1238, condition L Flexural Modulus ASTM D-1505Tensile strength at break ASTM D-412 Elongation at break ASTM D-412Hardness Shore D ASTM D-2240 Volume resistivity ASTM D-257 Power factorASTM D150 L.O.I. ASTM D-2863-77 Flame resistance UL-94 testing forclassification in Classes 94 V0, 94 V1, 94 V2

EXAMPLES

Some flame-proof formulations according to the invention and relatedcharacterization results are reported in Tables 1 and 2. Particularlysignificant are the compositions of Examples 3 and 4, which result quitesuitable for the insulation of electrical cables.

Table 3 presents a few comparison examples which in particular point outthe improvements in flame retardation properties obtained by usingmaleic anhydride as a filler compatibilizer, alone or preferablyassociated with polydimethylsiloxane to improve the dispersion of thefillers.

TABLE 1 Flameproof compositions Example 1 Example 2 Example 3 Example 4% by % by % by % by weight weight weight weight FORMULATION Heterophasic27 45 26 26 composition No. 1 Heterophasic 7 — 6 6 composition No. 2Maleic anhydride — 5 — — additive No. 1 Maleic anhydride — — 1.5 1.5additive No. 2 Magnifin H5 — 25 30 32.5 Securoc C 20 — — — Whitetex 20 —20 — Spinflam ML94M 25 25 15 32.5 Zn stearate — — 1.0 1.0 Lica 12 0.8 —— — Irganox B225 0.2 — 0.10 0.10 Irganox 1010 — 0.10 0.10 DSTDP (IrganoxPS802) 0.30 0.30 MIL g/min — — 0.24 0.31 PROPERTIES (compression moldedplaque) L.O.I. % 25.8 28 27.2 26.7 UL 94 (1.6 mm) class — — V0 V0 UL 94(3.2 mm) class V0 V2 V0 V0 Flexural Modulus N/mm² — — 780 595 Tensilestrength 6.5 10.3 7.9 6.2 at break (a) N/mm² Elongation at break (a) %180 355 200 233 Hardness Shore D points 52 45 47 44 (a) performed at 200mm/minute

TABLE 2 Electrical properties of some flameproof compositions.PROPERTIES Example 3 Example 4 PVC VOLUME RESISTIVITY Ohm × cm Ohm × cmOhm × cm AT 25° C. Initial (dry) 2400.e¹² 2000.e¹² 788.e¹²  1 day wet80° C.  594.e¹²  441.e¹²  7 day wet 80° C.  163.e¹²  87.e¹² 21 day wet80° C.  58.e¹²  22.e¹²  1 day wet 25° C. 728.e¹²  7 day wet 25° C.510.e¹² 21 day wet 25° C. 558.e¹² POWER FACTOR Tan Delta Tan Delta TanDelta Initial (dry)  0.32  0.50 7.64  1 day wet 80° C.  3.40  8.16  7day wet 80° C. 14.76 18.44 21 day wet 80° C. 16.35 16.35  1 day wet 25°C. 7.56  7 day wet 25° C. 7.46 21 day wet 25° C. 7.28

TABLE 3 Comparative examples Comparative Comparative ComparativeComparative Comparative example 1 example 2 example 3 example 4 example5 FORMULATION % by weight % by weight % by weight % by weight % byweight Heterophasic composition No. 1 40 38 36 32 30.8 Maleic anhydrideadditive No. 1 — 2 4 — 2 BY-27 — — — 8 7.2 Magnifin H5 60 60 60 60 60PROPERTIES (compression molded plaque) L.O.I. % 26.8 28.6 28 28.6 >35 UL94 (3.2 mm) class B V2 V2 B B

What is claimed is:
 1. Flame-proof polyolefin compositions comprising:A) from 20 to 60% by weight of a heterophasic olefin polymer compositioncomprising a crystalline olefin polymer (a) and an elastomeric olefinpolymer (b), said composition (A) being optionally modified with atleast one functional monomer in an amount from 0.005% to 0.6% by weightwith respect to the weight of the total composition; B) from 15 to 40%by weight of one or more inorganic hydrated fillers; C) from 12 to 40%by weight of one or more organic flame retardants containing nitrogen;and D) from 0 to 40% by weight of one or more inorganic anhydrousfillers.
 2. Flame-proof polyolefin compositions according to claim 1comprising: A) from 30 to 45% by weight of a heterophasic olefin polymercomposition comprising a crystalline olefin polymer (a) and anelastomeric olefin polymer (b), said composition (A) being optionallymodified with at least one functional monomer in an amount from 0.005%to 0.6% by weight with respect to the weight of the total composition;B) from 18 to 35% by weight of one or more inorganic hydrated fillers;C) from 22 to 35% by weight of one or more organic flame retardantscontaining nitrogen; and D) from 0 to 40% by weight of one or moreinorganic anhydrous fillers.
 3. Flame-proof polyolefin compositionsaccording to claim 1 comprising: A) from 30 to 45% by weight of aheterophasic olefin polymer composition comprising a crystalline olefinpolymer (a) and an elastomeric olefin polymer (b), said composition (A)being optionally modified with at least one functional monomer in anamount from 0.01% to 0.3% by weight with respect to the weight of thetotal composition; B) from 18 to 35% by weight of one or more inorganichydrated fillers; C) from 22 to 35% by weight of one or more organicflame retardants containing nitrogen; and D) from 10 to 25% by weight ofone or more inorganic anhydrous fillers.
 4. Flame-proof polyolefincompositions according to claim 1 wherein component A) is a heterophasiccomposition comprising (percent by weight): a) 10-60% of a propylenehomopolymer with an isotacticity index value, determined as percent byweight of the polymer insoluble in xylene at 25° C., higher than 80 orof a propylene crystalline copolymer with at least one of ethylene andC₄-C₁₀ alphaolefins containing at least 85% of propylene and having anisotacticity index value of at least 80, or of mixtures thereof; b)0-40% of a copolymer fraction containing ethylene and insoluble inxylene at 25° C.; and c) 15-90% of an ethylene copolymer with at leastone of propylene and C₄-C₁₀ alphaolefins, and optionally a diene, theethylene copolymer containing 20-60% of ethylene and being completelysoluble in xylene at 25° C.; said heterophasic composition having atotal content of ethylene from 15 to 60% by weight and being optionallymodified with the at least one functional monomer.
 5. Flame-proofpolyolefin compositions according to claim 4 wherein component A) is aheterophasic composition comprising (percent by weight): a) 20-50%, of apropylene homopolymer with an isotacticity index value, determined aspercent by weight of the polymer insoluble in xylene at 25° C., between90 and 98, or of a propylene crystalline copolymer with at least one ofethylene and C₄-C₁₀ alphaolefins containing at least 85% of propyleneand having an isotacticity index value of at least 80, or of mixturesthereof; b) 2-25%, of an essentially linear ethylene copolymercontaining from 0.5 to 20% by weight of at least one of propylene andC₄-C₁₀ alphaolefins; and c) 30-75%, of an ethylene copolymer with atleast one of propylene and C₄-C₁₀ alphaolefins, and optionally a diene,the ethylene copolymer containing 20-60% of ethylene and 0-10% of thediene and being completely soluble in xylene at 25° C.; saidheterophasic composition being optionally modified with the at least onefunctional monomer.
 6. Flame-proof polyolefin compositions according toclaim 4 having a value of the elongation at break equal to or higherthan 125%.
 7. Flame-proof polyolefin compositions according to claim 1wherein component B) is selected from the group consisting of magnesiumhydroxide, aluminum hydroxide, and mixtures of magnesium hydroxide andhydrated magnesium carbonate.
 8. Flame-proof polyolefin compositionsaccording to claim 1 wherein component C) is selected from the groupconsisting of 1,3,5-triazine, urea, dicyandiamide and organicderivatives from these compounds or their salts.
 9. Flame-proofpolyolefin compositions according to claim 8 wherein component C) isselected from the group consisting of melamine, acetoguanamine,benzoguanamine, ethyleneurea and ethylenethiourea.
 10. Flame-proofpolyolefin compositions according to claim 1 wherein component D) isselected from the group consisting of talc, calcined kaolin andinorganic carbonates.
 11. Flame-proof polyolefin compositions accordingto claim 10 wherein component D) is calcined kaolin.
 12. Flame-proofpolyolefin compositions according to claim 1 wherein the functionalmonomer optionally modifying component A) is selected from the groupconsisting of acrylic acid, methacrylic acid, itaconic acid, citraconicacid, fumaric acid, maleic acid and corresponding anhydrides and estersand unsaturated silanes.
 13. Flame-proof polyolefin compositionsaccording to claim 12 wherein the functional monomer is maleicanhydride.
 14. Flame-proof polyolefin compositions according to claim 1further comprising additives selected from the group consisting ofpigments, thermal antioxidants, ultraviolet absorbers, processing aids,filler dispersants, oils and waxes.
 15. Flame-proof polyolefincompositions according to claim 14 wherein the filler dispersants areselected from the group consisting of alkyltitanates andpolydimethylsiloxanes.
 16. Flame-proof polyolefin compositions accordingto claim 1 wherein: A) is a heterophasic composition according tocomponent A in claim 5, modified with maleic anhydride; B) is selectedfrom the group consisting of magnesium hydroxide and mixtures ofmagnesium hydroxide and hydrated magnesium carbonate; C) is melamine;and D) is calcined kaolin.
 17. Flame-proof polyolefin compositionsaccording to claim 16 further comprising additives selected from thegroup consisting of pigments, thermal antioxidants, ultravioletabsorbers, processing aids, filler dispersants, oils and waxes. 18.Flame-proof polyolefin compositions according to claim 17 wherein thefiller dispersants are selected from the group consisting ofalkyltitanates and polydimethylsiloxanes.